Generally, with reference to JP-7-186878A, a side impact detecting device is disclosed as a collision detection device for detecting a collision between a vehicle and an obstacle. The side impact detecting device has two cantilever beams and multiple side impact detecting sensors. The two cantilever beams are arranged in parallel in the vehicle front-rear direction between an outer panel of a door of the vehicle and an inner member of the door, in such a manner that the fixing ends of the cantilever beams are fixed to the inner member of the door.
The side impact detecting sensors are sensors which will become ON when being pressed. The side impact detecting sensors are arranged at the cantilever beam at the side of the outer panel of the vehicle door, and spaced from each other at a predetermined distance. When there occurs a collision between the vehicle door and an obstacle, the outer panel will be concaved toward the side of the inner member, so that the side impact detecting sensor attached to the cantilever beam is pressed to become ON. Thus, the collision of the vehicle can be detected.
However, in this case, even when there occurs the collision with the vehicle door, the collision cannot be detected until the side impact detecting sensor is pressed due to the deformation of the outer panel of the vehicle door. Thus, it is difficult to shorten the response time from the occurrence of the collision to the detection of the collision.